Directional relay



Dec. 19, 1967 c. A. GALLAGHER 3,359,417

DIRECTION/XL RELAY Filed Nov. 18, 1966 5 Sheets-Sheet 1 'lw 42) M 42 i46757 I 742i ATTORNE y' Dec. 19, 1967 C. A. GALLAGHER DIRECTIONAL RELAYFiled Nov. 18, 1966 I TlCIJlL/ 3 Sheets-Sheet 2 BY A ` ATTORN YS Dec.19, 19674 Filed Nov. 18, 1966 C. A. GALLAGHER 3,359,417

DIRECTIONAL RELAY 5 Sheets-Sheet Z United States Patent O 3,359,417DIRECTIONAL RELAY Cornelius A. Gallagher, Hicksville, N.Y., assigner toServo Corporation of America, Hicksville, N.Y., a corporation of NewYork Filed Nov. 18, 1966, Ser. No. 605,116 11 Claims. (Cl. 246-249) Thisapplication is a continuation-in-part of my copending application, Ser.No. 308,980, filed Sept. 16, 1963, now abandoned.

My invention relates to an improved relay device responsive to aparticular direction of vehicular-traffic motion to uniquely indicatethat the traffic is moving in that particular direction, and not in theopposite direction.

The invention has particular application to railroads, as for example ina region in approach to a highway grade crossing Where shunting orsorting operations are being conducted. Such `operations necessarilyinvolve train movement in first one and then the other direction, but ofcourse there is need to operate highway traflic signals to STOPcondition only if the train is actually going to cross the highway. Insome situations, the shunting operations are conducted between and onboth sides of two fairly closely spaced highway grade crossings, andthere is need to signal highway traflic to STOP only when the particularhighway is going to be crossed by the train.

It is accordingly an object to provide an improved directionallyresponsive relay construction.

Another object is to provide an improved relay subjected to railroadtrailic in both directions but operative to create a remote actuationsignal only in response to one to the exclusion of the other directionof traflic movement.

A further object is to provide an improved relay subjected to railroadtraflic in both directions and operative to create a first remoteactuation signal unique to traflc moving in a first direction and asecond remote actuation signal unique to traflic moving in a seconddirection.

Still another object is to meet the above objects with a construction inwhich operation will unfailingly mean response to the desired (and notto the undesired) direction of train movement.

Other objects and various further features of novelty and invention willbe pointed out or will occur to those skilled in the art from a readingof the following description in conjunction with the accompanyingdrawings. In said drawings, which show, for illustrative purposes only,preferred forms of the invention:

FIG. 1 is a circuit diagram schematically indicating components of oneform of my invention;

FIG. 1A is a fragmentary View, partially in section, and showing a wheeltrip positioned for response to a railroad-car wheel, the section beingin the plane lA-IA of FIG. 1;

FIG. 2 is a series of graphs depicting, on the same time base,voltage-pulse developments in the circuit of FIG. 1;

FIG. 3 is a diagram schematically indicating the relation of componentsin another form of the invention;

FIG. 4 is a series of graphs depicting, on the same base, voltage-pulsedevelopments in the circuit of FIG. 3;

FIGS. 5 and 5A are electrical diagrams schematically illustratingalternative embodiments of a form of the invention particularlyapplicable to electrified rail territory; and

FIG. 6 is a collection of graphs depicting voltage relationships in theembodiments of FIGS. 5 and 5A.

Briefly stated, my invention contemplates detection ice of a .particularone direction of rail-traffic movement, in

the presence of random movement in both directions past a givenmonitoring locat-ion. Basic response to train movement is developed bytwo closely spaced wheel-trip 5 devices, which are preferably of thevariety described in United States Letters Patent No. 3,151,827, issuedOct. 6, 1964, but which in any event present to passing carwheel flangesa permanently magnetized air gap, so that an electric pulse output of afirst polarity is produced as the wheel enters the gap and a similarpulse of opposite polarity is produced as the flange leaves the gap. Bylongitudinally spacing the air gaps of the two wheel trips such that forany given passing aXle the second pulse for the first trip coincides intime with the first pulse for the second trip, and by utilized suitablypolarized coincidencedetection means, it is possible to uniquelyidentify one (to the exclusion of the other) direction of trainmovement. Alternatively, where desired, each of the directions of trainmovement can be uniquely identified, for such remote signaling oractuating purposes as may be necessary.

In the form shown in FIGS. 1 and 2, the invention utilizes wheel tripswhich are each connected to the coincidence-detection means inoppositely polarized manner so that the detected coincidence involveslike-polarity pulses of the respective wheel trips for a given directionof movement of a passing wheel. In the form of FIGS. 3 and 4, the wheeltrips are each connected to the coincidence-detection means in likepolarized manner whereby the detected coincidence involves the positivepulse of one wheel trip and the negative pulse of the other wheel tripfor a given direction of passing traflic.

Referring to FIGS. 1 and 2, the invention is shown in application to alength of railroad track comprising two spaced rails 10 andaccommodating rolling stock, such as a freight car having a truck 11, ajournal box 12 and a wheel 13. The flange 14 of the wheel rides insidethe railhead, as shown more particularly in FIG. 1A.

Secured to the web of the rail 10 at locations spaced by the amountdesignated D are first and second wheel trips schematically indicated at21S-16 in FIG. 1. For the View of FIG. l, the web of the rail will maskthe wheel trips 15-16 because they are secured inside the web, but therectangular outlines at 15-16 will be understood to suggest the pottedplastic confines of the two wheel trips, as described in greater detailin said copending application. It suffices for present purposes toexplain in connection with FIG. 1A that the permanently polarized airgap cut by the flange 14 is established by a permanent magnet, such as ahorseshoe magnet 17 secured to the web of the rail. Magnet 17establishes the polarized air gap between the outer leg of the magnetcore and the adjacent side of the railhead. A coil linked to the core 17develops, at output connection 18, a pulse or fluctuating electricalsignal as each car wheel flange enters into or departs from the air gap.Such voltage fluctuations are depicted in the two curves a and b of FIG.2.

In curve a (FIG. 2), there is illustrated the response of the firstWheel trip 1S to the passage of the Wheel 13 from right to left in thesense of FIG. 1; curve b illustrates the response of the second wheeltrip 16 to the passage of the wheel 13 from right to left in the senseof FIG. l. On the flange 14 entering the air gap for the first wheeltrip 15, a negative pulse 19 is developed at output connection 18. Thispulse reaches its negative peak before the flange has fully entered theair gap and proceeds to drop back to zero and to cross the axis in thedevelopment of a positive pulse 20 as the flange 14 leaves the air gap.In like manner, the same wheel flange 14 entering the air gap for 70 thesecond wheel trip '16 will first develop a negative pulse 21, and uponleaving the same, will develop a positive pulse 22.

The spacing D between wheel trips 15-16 is such in relation to standardwheel sizes that the second pulse 2? for the first wheel trip 15 willsubstantially coincide in time with development of the first pulse 21for the second Wheel trip 16 on a freight car wheel, which is the usualsituation encountered on a railroad track. The spacing D is preferablyten inches, but it will be appreciated that the duration of pulsesproduced by wheel trips of the character indicated is great enough sothat time-coincidence for the oppositely polarized pulses 20-21 canoccur for a variety of passing wheel anges and ange heights.

As explained briefly above, the for-m of FIGS. l and 2 demonstrates likeconnection of the two wheel trips to the coincidence-detection system,meaning that reliance is placed upon the polarized nature of theoppositely polarized pulses 2ii-21 for which coincidence is to beobserved. For the right-to--left traiiic direction, FIG. 2 shows thatthe desired time coincidence involves the positive pulse 20 (curve a)while the curve b pulse 21 is negative. However, for the reversedirection of trailic, namely,

from left to right in the sense of FIG. l, the first wheel trip todevelop a signal will be the wheel trip 16, so that the pulse 21 forwheel trip 16 will first be developed; this is followed by a timecoincidence between the second pulse 22 (positive) of wheel trip 16 withthe first pulse 23 (negative) of wheel trip 15, there being no timecoincidence for the positive pulse 24 developed by wheel trip 15. Thus,whatever the direction of traffic, time coincidence involves oppositelypolarized pulses, but the sense of the difference between these pulsesis unique in one polarity for left-toright movement and in oppositepolarity for right-to-left movement.

In FIGS. 1 and 2, the coincidence detection mechanism utilizesinterconnected relays 25-28, each of which is connected to a differentone of the wheel trips; these relays are each shown as of thedouble-pole, double-throw variety, and it will be understood that, foreach relay shown,

two like single-pole relays may be connected with their windings inparallel to achieve the same result. The solenoid means for the relay 25connected to the wheel trip actuates two contact arms 26-27, and thesolenoid for the other such relay 28 actuates two similar arms 29-30.For any given single direction of tratiic movement to be monitored, onlyone pole of each of the relays 25-23 need be utilized. Thus, for theright-to-left detection situation, the back contact 31 of relay 25 isconnected with the front contact 32 of relay 28, and no connections areprovided for the front contact 33 of relay 25 or for the back contact 34of relay 28. When the two relays 25-28 are suitably actuated, as in thepresence of the second or positive pulse of wheel trip 15, and the firstor negative pulse 21 of wheel trip 16, the circuit is completed via theconnection 35 to a relay coil 36 which, in turn, serves to actuate acontrol relay 37 for remotely actuating or indicating the right-to-left(R-L) traic direction response. In the form shown, the particularcircuit to the coil for relay 36 utilizes a direct-current source 38, asuitable proi tective resistor 39, and storage means 40 with aprotective diode 41 to assure operation of the coil 36 only by pulses ofdesired polarity. The storage means 40 assures a predeterminedholding-in of the contact arm 38 of relay 36 after the coincidence ofpulses 20-21 has terminated.

For detection of traffic in the left-to-right sense of FIG. l, meaningthat wheel trip 16 is first operated and that the coincidence of pulses22-23 is to be detected, I employ the other pole of each of the relays25-28. Thus, the coincidence-detector connection for this situationinvolves the back contact 43 for arm 30 of relay 28, and the frontcontact 44 for arm 27 of relay 25, the remaining contacts 45-46 beingnot utilized. The relay system for remote indication or control may beas described for the right-to-left direction situation, and therefore Iemploy the same source 3S to excite the relay coil 47 which willcomplete a circuit through its contact arm 47 to the control relay 48,upon time-coincidence of the pulses 22-23, meaning that left-to-right(L-R) traiiic movement has been detected.

Because of the nature of the described coincidencedetection connectionsfor the contacts of the relays 25-28, it will be appreciated that anymalfunction in the circuit will serve merely to avoid actuation ofeither of the control relays 37-38. Thus, if these relays are operatedat all, they correctly indicate the detected direction of traiiicmovement, and no false indications are developed with this circuit.

The arrangement of FIGS. 3 and 4 operates on the principle of detectingtime-coincidence between pulses of like polarity developed by the twowheel trips 15-16, which have been designated WT-1 and VVT-2 in FIG. 3.This means that the output-circuit connections from wheel trips 15 and16 will be connected to their respective coincidence-detection circuitsin oppositely poled relation, as distinguished from FIGS. l and 2,wherein the wheel trips 15-16 have like-polarized connections to theircoincidence detection circuits.

In the arrangement of FIGS. 3 and 4, coincidence detection involves thesummation of two signals occurring at the same time, and thereforesimple pulse shaping is involved, in order that varying train speeds andange heights shall not impair desired operation. Pulse shaping isschematically indicated for the case of wheel trip 16 by a rst positivepulse limiter 5t) and by a second or negative pulse limiter 51.Similarly, a negative pulse limiter 52 and a positive pulse limiter 53are connected to the output of wheel trip 15. The action of these pulselimiters to 53 will be understood by reference to the curves of FIG. 4.v

In curve a (FIG. 4) there is illustrated in solid outline (traflicproceeding left-to-right) the succession of pulse-output development forthe Wheel trip 16 being a positive pulse 54 followed by a negative pulse55 as the wheel flange leaves its air gap. Because the wheel trip 15 isoppositely connected to its coincidence-detection circuit, as comparedwith the connections for wheel trip 16, curve b shows the rst pulse ofwheel trip 15 as a negative pulse 56 followed by a second or positivepulse 57. It is the coincidence of the two negative pulses -56 whichsignifies left-to-right traffic movement. These signals have beenschematically indicated as B and C and they ultimately operate theleft-to-right (L-R) responsive control relay 58.

For traiiic moving in the opposite direction, that is from right toleft, curve b of FIG. 4 signifies that wheel trip 15 will develop itssecond or positive pulse 57 in time-coincidence with the iirst orpositive pulse 59 of wheel trip 16. These two pulses have beendesignated D and A, lrespectively, in FIG. 3, and it is theright-to-left (R-L) responsive control relay 60 which will ultimatelyrespond-to this coincidence of positive pulses. For this direction oftrain movement, the second or negative pulse 55 of wheel trip 16 is notutilized.

In order that the coincidence detectors may function from thetime-coincidence of two pulses of like polarity, they are, as indicated,shaped to uniform amplitude or magnitude suggested by the curves c and dof FIG. 4. The amplitude M chosen for such shaping applies both forpositive and for negative pulses and has been so indicated by legends oncurves c and d. This amplitude should be at such a relatively low levelthat no matter how slow the passing train, or how new (i.e. not worn)the wheel (meaning that the ange 14 does not project far from the wheelrim), there will still be adequate signal developed for a passing flangeto permit of some degree of pulse limiting. The net result of limitingis to create flattopped signals for each of the pulses. Thus, thepositive pulse 54 shown in curve a becomes the fiat-topped positivepulse 64 in curve c, and the negative pulse 55 of curve a becomes theat-topped'negative pulse 65 in curve c. In curve d, the negative pulse56 becomes the flat-topped negative pulse 66, and the positive pulse 57becomes the fiat-topped pulse 67. The flat-topped pulses 69 and 65' willbe understood to correspond to the pulses 59-55 of curve a.

The signals labeled A, B, C, D in FIG. 3 will be understood tocorrespond respectively to the fiat-topped signals described inconjunction with curves c and d, and thus for right-to-left (R-L)traffic detection, the coincidence detector 70 responds to signals A andD by adding them, and the control relay 60 functions upon detection of asignal exceeding the threshold preset by means 71 to a level greaterthan amplitude M and less than amplitude 2M. In like manner, theleft-to-right concidence-detection functions at 72 involve summation ofthe two negative pulses B and C, and if these occur at the same time,meaning left-to-right traffic movement, the control relay 58 will becaused to operate because a signal exceeding the threshold set at 73will have been detected.

In FIGS. 5 and 6, I illustrate application of principles of theinvention to situations in which spurious signals may cause ambiguousoperation, as for example in electried territory, where the rail isrelied upon to carry heavy currents, causing undesired induced voltagesin both wheel-trip devices, such as the spaced trips X-Y. Trips X-Y maybe of the nature previously described in connection with FIG. lA, but toneutralize spurious induced voltages of the character indicated, thewindings of trips X-Y are effectively connected back-to-back. This maybe accomplished, for example, by using similar devices X-Y which havetheir output windings linked in opposite sense to their respectivepolarized cores, and by then connecting the coil outputs in parallel;alternatively, and as shown in FIG. 5, the turns of the respectivewindings Of trips X-Y may be in the same direction of coupling to theirrespective polarized cores, in which case the coil outputs are connectedin phase-opposition. The net result of so connecting the electricaloutputs of trips X-Y is to not only neutralize the undesired inducedvoltages but also to make the interconnection of these windings anintegral part of the coincidence-detection means which characterize theinvention. This result more clearly appears from the diagrams of FIG. 6.

The solid curve at FIG. 6a may typically represent the electricalresponse of one of the wheel trips (X) to the passage of a wheel; thisresponse may thus be characterized by a negative swing or pulse 80 (asthe wheel ange enters the polarized air gap) followed by a positiveswing or pulse 31 (as the wheel flange leaves the air gap). Now, if apulse such as has been described at Sil-81 should develop due to somerail current, rather than due to a wheel movement past trip X, the othertrip Y will simultaneously induce precisely the same spurious wave formbut due to the effective back-to-back connection of the windings oftrips X-Y these two like induced voltages will cancel each other; thedashed waveshape 82-83 in FIG. 6a suggests the equal and oppositerelation of such simultaneously induced spurious voltages at XeY, andtheir self-cancelling relationship.

On the other hand, as has already been pointed out, the spacing Dbetween wheel trips X-Y means a particular physical time differencebetween the positive and negative swings of the trip--output voltages.If trip X is rst traversed by a wheel, then the swings 84-85 for trip Ywill follow the swings 80-81 for trip X, in the general time relationillustrated by solid lines in FIGS. 6a and b; and, by virtue of thedescribed interconnection of the output windings of trip XY, the secondpulse of the firsttraversed trip (X) coincides with and is of the samepolarity as the first pulse of the second-traversed trip (Y). This factand the result flowing therefrom are demonstrated in FIG. 6c, whereinthe two positive pulses 8184 indicate the desired coincidence byappearing as a new pulse 86 of double magnitude, the minor leading andtrailing pulses 80-85' corresponding to the noncoincident remainders ofvoltage development at trips XY.

y The foregoing discussion in connection with curve c of FIG. 6 will beunderstood to apply for the directional situation in which a wheeltraverses trip X before it traverses trip Y. For traicin the oppositedirection, trip Y will be first traversed, so that the coincident pulsesare negative, producing the large negative pulse 87, between minorleading and trailing pulses 84-81 corresponding to the non-coincidentremainders of voltage development at trips X-Y.

Thus, it is seen that the desired coincidence is effected and recognizedfor interconnected wheel-trip outputs. Viewed in one aspect, thetraffic-direction information is inherent in the polarity of the centralor major pulse 86 or 87, as the case may be; viewed in another aspect,the traffic-direction information is inherent in the polarity pattern ofa train of three alternating pulses. Depending upon the aspect withwhich the output information is viewed, suitable logic circuitry may beemployed to actuate the correct R-L or L-R control relay, for thedetected direction of traffic `movement.

FIG. 5 schematically illustrates a situation in which directionalinformation is extracted on the basis of identifying the large centralpulse (86 or 87) and its polarity. For a first polarity, a rst rectifierand storage circuit 88-89 is connected to store the peak voltage (in thecombined outputs of trips XY) while a second and oppositely poledrectifier and storage circuit 90-91 is connected to store the peak forthe opposite polarity, These peak voltages are differentially evaluatedby simultaneously discharging the storage circuits through a read-outvoltage divider or summing resistor 92. Read-out is accomplishedmomentarily closing a contact 93 to ground, at the conclusion of eachcluster of three pulses; FIG. 5 suggests accomplishment of thissynchronizing function by utilizing a full-wave rectifier (effectively a3pulse counter) 94, in conjunction with wave-shaping means 95, to form asquare wave for each group of three pulses (80-868S, or 8487-81'), thenrectifying the differentiated square wave to obtain an end-markingsynchronizing pulse to energize coil 98 for the read-out contacts 93.The R-L and L-R responsive control relays 58'60 are suitable polarizedto respond to the polarity of the read-out pulse whch develops acrossresistor 92 upon read-out.

FIG. 5A schematically illustrates a situation in which directionalinformation is extracted on the basis of identifying the polaritypattern of the generated 3-pulse cluster (80-86-85, or 8487-81). Agate-open square wave for gate 100 is generated by rectifier 94 and waveshaper 95, which is effective to pass limited positive pulses (at 101)and limited negative pulses (at 102) to suitably poled two-pulsecounters 10S-104. Thus, for a given gate-open condition, one or theother (but not both) of counters 10S-104 will achieve its count of two,which may be effective to change its state and thus activate thecorresponding direction-indicating control relay 58 or 60, as will beunderstood.

It will be seen that I have described a relatively simple relayconfiguration for uniquely detecting and displaying, and for remotelyindicating or actuating suitable devices in accordance with thedetection of a single particular direction of traffic movement. Whetherthe coincidence depends upon simultaneous connection of two oppositelypolarized pulses, or upon the simultaneous detection of two likepolarized pulses, the response to a given direction of traffic movementis unique. If desired, response to both directions may be yachieved withindications unique to each of the two directions. Basically, all of thedescribed forms are inherently simple and foolproof and make use ofinherent polarizing properties in the signal development from themagnetic wheel trips and their connections to the coincidence-detectionmeans.

While I have described the invention in connection with the preferredforms shown, it will be understood that the principles of the inventionmay involve modifications without departing from the spirit of theinvention as defined in the claims which follow.

What is claimed is:

1. Relay means responsive to a particular one direction of trafficmovement along a railroad track, comprising two rail-mounted magneticwheel-trip devices secured in spaced relation along the same track, eachof said devices presenting a magnetized air gap for interception of awheel flange and developing an electrical output signal characterized by-a -pulse of one polarity Ifollowed by a pulse of opposite polarity foreach passing wheel, the spacing between said trips being such that awheel ange on a given axle is leaving the gap for one wheel trip as awheel flange on the same axle is entering the gap for the other wheeltrip, whereby for each passing axle proceeding in a first directionthere will be a coincidence of pulse outputs of said trips in a firstunique polarized relationship, and further whereby for each passing axleproceeding in the opposite direction there will be a coincidence ofpulse outputs of said trips in a second unique polarized relationship,and coincidence-detection means including a control relay responsive todetection of the coincidence in said first unique polarized relationshipfor producin-g a signal for remotely indicating that the passing trafficis in said rst direction.

2. Relay means according to claim 1, and including additionalcoincidence-detection means including a further control relay responsiveto detection of the coincidence in said second unique polarizedrelationship for producing a signal for remotely indicating that thepassing traffic is in said opposite direction.

3. Relay means according to claim 1, in which each of said wheel-tripdevices includes an electrical output winding, saidcoincidence-detection means including means interconnecting saidwindings in phase-opposition, whereby rail currents or the like actingsimultaneously to induce corresponding voltages in both said windingswill be effectively neutralized by said interconnection, and wherebysaid pulse coincidence will result in adding like-polarity pulse outputsof said windings, said like polarity being uniquely representative ofthe instantaneous direction of traffic movement.

4. Relay means responsive to a particular one direction of trafficmovement along a railroad track, comprising two rail-mounted magneticwheel-trip devices secured in spaced relation along the same track, eachof said devices presenting Ia magnetized air gap for interception of aWheel ange, the spacing between said trips being such that a wheelflange on a given axle is leaving the gap for one wheel trip las a wheelflange on the same axle is entering the gap for the other wheel trip,two separate double-throw relays having actuating coils connectedsimilarly to each of said wheel trips, and output relay means includingan excitation circuit requiring for its operation the completion of acircuit through the back contact of one of said double-throw relays andthe front contact of the other of said double-throw relays.

5. Relay means according to claim 4, in which said last-defined meansincludes a storage circuit connected to receive its charge uponcoincident closure of said back and front contacts, said storage circuitbeing effective to sustain a given actuation of said output relay meansfor a predetermined length of time after said coincident closure hasterminated.

6. Relay means responsive ot a particular one direction of trafficmovement along a railroad track, comprising two rail-mounted magneticwheel-trip devices secured in spaced relation along the same track, eachof said devices presenting a magnetized air gap for interception of awheel ange, the spacing between said trips being such that la wheel angeon a given axle is leaving the gap for one wheel trip as a wheel flangeon the same axle is entering the gap for the other wheel trip, twoseparate doublepole double-throw relays having actuating coils connectedsimilarly to each of said Wheel trips, first output-relay meansincluding an excitation circuit requiring for its operation thecompletion of a circuit through the back contact of a first pole of oneof said double-throw relays and the front contact of a first pole of theother of said double-throw relays, and second output-relay meansincluding an excitation circuit requiring for its operation thecompletion of a circuit through the front Contact of the second pole ofsaid one double-throw relay and the back contact of the second pole ofsaid other double-throw relay.

7. Relay means responsive to a particular one direction of trafficmovement |along a railroad track, comprising two rail-mounted magneticWheel-trip devices secured in spaced relation along the same track, eachof said devices presenting a magnetized air gap for interception of awheel flange and developing and electrical output signal characterizedby a pulse of one polarity followed by a pulse of opposite polarity foreach passing wheel, the spacing between said trips being such that awheel flange on a given axle is leaving the gap for one wheel trip as awheel flange -on the same axle is entering the gap for the other wheeltrip, whereby for each passing axle proceeding in a first directionthere will be a coincidence of pulse outputs of said trips in la firstunique polarized relationship, and further whereby for each passing|axle proceeding in the opposite direction there will be a -coincidenceof pulse outputs of said trips in a second unique polarizedrelationship, and coincidence-detection means including a control relayresponsive to detection of the coincidence in said first uniquepolarized relationship for producing a signal for remotely indicatingthat the passing trahie is in said first direction, -said wheel tripsbeing connected to said coincidence-detection means in like-polarizedmanner, wherebythe detected coincidence involves the positive pulse ofone wheel trip and the negative pulse of the other wheel trip for afirst direction of passing traic.

8. Relay means responsive to a particular one direction of trafficmovement lalong a railroad track, comprising two rail-mounted magneticwheel-trip devices secured in spaced relation along the same track, eachof said devices presenting a magnetized air gap for interception of aWheel flange and developing an electrical output signal characterized bya pulse of one polarity followed by a pulse of opposite polarity foreach passing wheel, the spacing between said trips being such that awheel flange on a given axle is leaving the gap for one wheel trip as awheel flange on the same axle is entering the gap for the other wheeltrip, whereby for each passing axle proceeding in a first directionthere will be a coincidence of pulse outputs of said trips in a rstunique polarized relationship, and further whereby for each passing'axle proceeding in the opposite direction there will be a coincidenceof pulse outputs of said trips in a -second unique polarizedrelationship, and coincidence-detection means including a control relayresponsive to detection of the coincidence in said first uniquepolarized relationship for producing a signal for remotely indicatingthat the passing traic is in said first direction, said wheel tripsbeing connected to said coincidence-detection means in oppositelypolarized manner, whereby the detected coincidence involves likepolaritypulses of said respective wheel trips for a given direction of passingtraffic.

9. Relay means according to claim 8, in which said coincidence-detectionmeans comprises signal-amplitude limiting means set to limit saidlike-polarity pulses to essentially one given level which is less thanthe maximum wheel trip pulse amplitude for the slowest movinganticipated traflic, and said control relay includes means set tooperate upon detection of a threshold input signal representing the sumof said like-polarity pulses, said threshold level being intermediatesaid given level and twice said given level.

10. Relay means responsive to a particular one direction of trafiicmovement along a railroad track, comprising two rail-mounted magneticwheel-trip devices secured in spaced relation along the same track, eachof said devices presenting |a magnetized air gap for interception olf awheel ange and developing an electrical output signal characterized by`a pulse of one polarity followed by a pulse of opposite polarity foreach passing wheel, the spacing between said trips being such that awheel flange on a given axle is leaving the gap for one wheel trip as awheel flange on the same axle is entering the gap for the other wheeltrip, whereby for each passing axle proceeding in a first directionthere Will be a coincidence of pulse outputs of said trips in a firstunique polarized relationship, and further whereby for each passing axleproceeding in the opposite direction there will be a coincidence ofpulse outputs of said trips in a second unique polarized relationship,first coincidencedetection means including a control relay responsive todetection of the coincidence in said first unique polarized relationshipfor producing a signal for remotely indicating that the passing traic isin said first direction and additional coincidence-detection meansincluding a further control relay responsive to detection of thecoincidence in said second unique polarized relationship for producing asignal for remotely indicating that the passing traic is in saidopposite direction; said wheel trips being connected to said firstcoincidence-detection means in oppositely polarized manner, whereby thedetected coincidence involves positive pulses of said wheel trips forone direction of passing traffic; and said wheel trips being alsoconnected to said additional coincidence-detection means in -oppositelypolarized manner, whereby the detected coincidence involves negativepulses of said wheel trips for the opposite direction of passingtraffic.

11. Relay means responsive to a particular one direction of traicmovement along a railroad track, cornprising two rail-mounted magneticwheel-trip devices secured in `spaced relation along the same track,each of said devices presenting a magnetized lair gap for interceptionof a wheel flange and developing an electrical output signalcharacterized by a pulse of one polarity followed by a pulse of oppositepolarity for each passing wheel, the spacing between said trips beingsuch that a wheel flange on a given axle is leaving the gap for onewheel trip as a wheel flange on the same axle is entering the gap forthe other wheel trip, whereby for each passing axle proceeding in afirst direction there will be a coincidence of pulse outputs of saidtrips in a rst unique polarized relationshi and further whereby for eachpassing axle proceeding in the opposite direction there will be -acoincidence of pulse outputs of said trips in a second unique polarizedrelationship, and coincidencedetection means including meansinterconnecting the outputs of said windings effectively inphase-opposition, whereby rail currents or the like actingsimultaneously to induce corresponding voltages in both said windingswill be effectively neutralized by said interconnection, and wherebysaid pulse coincidence will result in adding likepolarity pulse outputsof said windings, said like polarity being uniquely representative ofthe instantaneous direction of traffic movement.

References Cited UNITED STATES PATENTS 2,760,182 8/1956 Rechten et al.340-38 3,144,225 8/ 1964 Suerkernper et al. 246-247 X 3,210,539 10/1965Malaguin 246-249 FOREIGN PATENTS 1,147,728 6/ 1957 France.

ARTHUR L. LA POINT, Primary Examiner. S. T. KRAWCZEWICZ, Examiner.

1. RELAY MEANS RESPONSIVE TO A PARTICULAR ONE DIRECTION OF TRAFFICMOVEMENT ALONG A RAILROAD TRACK, COMPRISING TWO RAIL-MOUNTED MAGNETICWHEEL-TRIP DEVICES SECURED IN SPACED RELATION ALONG THE SAME TRACK, EACHOF SAID DEVICES PRESENTING A MAGNETIZED AIR GAP FOR INTERCEPTION OF AWHEEL FLANGE AND DEVELOPING AN ELECTRICAL OUTPUT SIGNAL CHARACTERIZED BYA PULSE OF ONE POLARITY FOLLOWED BY A PULSE OF OPPOSITE POLARITY FOREACH PASSING WHEEL, THE SPACING BETWEEN SAID TRIPS BEING SUCH THAT AWHEEL FLANGE ON A GIVEN AXLE IS LEAVING THE GAP FOR ONE WHEEL TRIP AS AWHEEL FLANGE ON THE SAME AXLE IS ENTERING THE GAP FOR THE OTHER WHEELTRIP, WHEREBY FOR EACH PASSING AXLE PROCEEDING IN A FIRST DIRECTIONTHERE WILL BE A COINCIDENCE OF PULSE OUTPUTS OF SAID TRIPS IN A FIRSTUNIQUE POLARIZED RELATIONSHIP, AND FURTHER WHEREBY FOR EACH PASSING AXLEPROCEEDING IN THE OPPOSITE DIRECTION THERE WILL BE A COINCIDENCE OFPULSE OUTPUTS OF SAID TRIPS IN A SECOND UNIQUE POLARIZED RELATIONSHIP,AND COINCIDENCE-DETECTION MEANS INCLUDING A CONTROL RELAY RESPONSIVE TODETECTION OF THE COINCIDENCE IN SAID FIRST UNIQUE POLARIZED RELATIONSHIPFOR PRODUCING A SIGNAL FOR REMOTELY INDICATING THAT THE PASSING TRAFFICIS IN SAID FIRST DIRECTION.